This invention relates to a transistor amplifier.
A current feedback type grounded emitter amplifier in which the emitter of a transistor is connected to a resistor is a known type of transistor amplifier. Such a transistor amplifier is shown in FIG. 1, where the emitter of a transistor Q.sub.1 is connected through a resistor R.sub.E to a negative electric source -B. The collector of the transistor Q.sub.1 is connected through a collector load resistance R.sub.C to a positive electric source +B. An input signal Vi applied to the base is provided as an output V.sub.O at the collector.
If it is assumed that the parameter h.sub.FE of the transistor Q.sub.1 which is an amplifying element in a circuit 1 is sufficiently high, then the collector current I.sub.C is substantially equal to the emitter current I.sub.E. If this current is represented by I.sub.O , then the following equation (1) can be established: EQU I.sub.0 =(V.sub.i -V.sub.BE1)/R.sub.E ( 1)
where, V.sub.BE1 is the base-emitter voltage of the transistor Q.sub.1.
The output voltage V.sub.O can be expressed by the following equation (2): EQU V.sub.O =+B-I.sub.O R.sub.C ( 2)
From the equations (1) and (2), the following equation (3) can be obtained: ##EQU1##
As indicated in equation (3), the output voltage of the amplifier circuit shown in FIG. 1 includes a so-called distortion component ##EQU2## in addition to its original output ##EQU3## This is due to the non-linearity of the transistor. Since the base-emitter voltage V.sub.BE1 is in a non-linear relation with the current I.sub.O, the amplifier of this type has essentialy this distortion component.
A method of applying negative feedback is known in order to eliminate such a distortion component. However, the application of negative feedback results in the reduction of the amplification degree of the circuit, and accordingly it is necessary to employ a number of amplifying elements to obtain a desired amplification degree to overcome the effects of the negative feedback.